In many applications, it is highly desirable to employ detectors to sense optical radiation throughout an extremely broad field-of-view. Typical examples include the use of electro-optic sensors for detecting motion, or the outbreak of a fire based on changes in infrared radiation levels detected over wide areas of coverage.
The use of internally reflecting truncated cones, pyramidal mirrors, spherical-parabolic surfaces and similar elements for field-of-view expansion and other control purposes is known. Examples of the same are given in U.S. Pat. Nos. 3,413,468; 3,551,676; 4,220,859; 4,778,996; and 4,831,259. The achievement of very wide coverage with available detectors, however requires the use of external lenses and/or reflectors, or the use of multiple detectors in conjunction with lenses and/or mirrors.